Download Senecio flaccidus Less. threadleaf groundsel

Senecio flaccidus Less.
ASTERACEAE
Synonyms:
threadleaf groundsel
S. douglasii DC.
Nutt. var. jamesii Torr. & Gray, and S. longilobus
Benth. This variety tends to be more uniformly
white hairy with the column of the flower head
narrower (8 to 10 mm wide at summit). Variety 2:
S. flaccidus Less. var. douglasii (DC) B. Turner &
T. Barkley, with two synonyms; S. douglasii DC
var. douglasii, and S. warnockii Shinners. This
variety is not white hairy throughout and the heads
are wider (10 to 15 mm). Variety 3: S. flaccidus
Less. var. monoensis (Greene) B. Turner & T.
Barkley, with two synonyms; S. douglasii DC var.
monoensis (Greene) Jeps., and S. monoensis
Greene. This variety is generally hairless
throughout, more herbaceous, and has a more
comb-like leaf, the linear lobes curling upward.
General Description.—Threadleaf groundsel is
also known as threadleaf butterweed, Douglas
groundsel or ragwort, felty groundsel, sand wash
groundsel, comb butterweed, old man, yerba cana,
squawweed, creek senecio, and cenicillo (Elmore
1976, Epple 1995, Stubbendieck and others 1997).
This species commonly reaches heights of 80 to
130 cm and under ideal conditions may reach 2 m.
It is probably best classified as a subshrub. It
forms woody stems to a meter or so but often dies
back to less than 50 cm from the ground-line. It
tends to become somewhat straggly as branches
may lean over in different directions, some
becoming almost decumbent. The leaves are
alternate, pinnately compound (sometimes not
divided), narrow and thread-like, up to 12 cm in
length, and usually covered with whitish hairs
giving the plant an obvious grayish color (Carter
1997, Ivey 1995, Kearney and others 1951, Martin
and Hutchins 1980-81). It may have some
tendencies to be evergreen in the southern portion
of its range.
Taxonomy.—There has been a profusion of
taxonomic names and varietal subclassifications
attached to this species, making for a complicated
taxonomy. The oldest specific name applied to this
species complex is now known to be Senecio
flaccidus Lessing (Turner and Barkley 1990).
Three varieties are recognized with the following
synonymies (Allred 2002, Kartesz 1994). Variety
1: S. flaccidus Less. var. flaccidus, with four
synonyms; S. douglasii DC var. longilobus
(Benth.) L. Benson, S. filifolius Nutt., S. flaccidus
Range.—Threadleaf groundsel occurs from
western Texas, west through New Mexico,
Arizona, to California, north to Wyoming and
Nebraska, Utah, and Nevada, and south into
northern Mexico. It is a wide ranging species
occurring in a variety of soil types and elevations
from about 760 to 2,440 m.
Ecology.—This species grows in short grass
prairies of the southwestern Great Plains and a
wide variety of scrubland and grassland habitats in
the Southwest. It has been considered a diagnostic
or climax species for desert grassland (DickPeddie 1993). It tends to become more abundant in
disturbed habitats and overgrazed rangelands and
often grows in washes. It is a taprooted plant that
grows relatively quickly and tends to be a shortlived perennial shrub to subshrub. Oxygen flux, as
it relates to photosynthesis, from leaves and twigs
was constant with increasing drought stress, up
until leaf drop occurred (Ehleringer and Cooper
1992). Twigs may serve to maintain some
photosynthesis through drought periods when new
foliage cannot easily be produced, such as during
dry springs and early summers. Threadleaf
groundsel was one of several shrub and subshrub
species, studied in Mojave and Sonoran desert
areas that generated substantial net carbon gains
from twig photosynthesis (Comstock and others
1988).
Reproduction.—Threadleaf groundsel generally
blooms in the late summer and fall but will bloom
earlier in the summer if sufficient moisture is
available. It produces numerous yellow flower
heads with eight to 17 ray florets, the rays 10 to 15
mm long (Carter 1997, Martin and Hutchins 198081). Seeds (fruits) are wind-borne with a white
fluffy pappus.
References
Growth
and
Management.—Threadleaf
groundsel is a fast growing, short lived perennial.
Plants may live 3 to 6 years or more. It increases in
rangelands as a result of overgrazing pressure. Its
abundance may be controlled through proper
grazing management and careful use of herbicides.
Spraying with 2,4-D has been used to control this
species.
Carter, J.L. 1997. Trees and Shrubs of New
Mexico. Johnson Books, Boulder, CO. 534 p.
Benefits and Disadvantages.—Because this
species will colonize open disturbed areas, it helps
achieve a quick ground cover in a natural
succession process. The perennial nature of the
plant further helps stabilize soil for longer-lived
perennials to eventually become established.
Direct human uses are minimal, but it was once
used medicinally by Native Americans. It is a poor
forage plant for cattle and horses and is known to
be toxic (Gay and Dwyer 1998, Stubbendieck and
others 1997, Warnock 1974) and causes liver
damage when consumed in large quantities
(Kirkpatrick 1992). All parts of the plant are
poisonous, younger leaves more so, and poisoning
is more of a problem on drier range conditions.
Symptoms in cattle may include a dry scaly nose, a
rough coat, and continuous walking with no
direction (Phillips Petroleum Company 1963).
Because it has low palatability, it tends to be
avoided except during long droughts or in heavily
overgrazed areas where it may increase in
abundance (USDA 1937). Toxicity of threadleaf
groundsel may be attributed to the pyrrolizidine
alkaloids (PA). About 50 percent of all identified
PA are toxic, and some are carcinogenic in rodents
(Stegelmeier and others 1999). Threadleaf
groundsel contains the pyrrolizidine alkaloids:
senecionine,
seneciphylline,
florosenine,
otonecine-based florosenine, and retrorsine
(Cooper and others 1996). As with many toxic
plants, concentration and preparation are critical
factors. For example, the Navajo would boil entire
plants and drink the mixture to assist the voice and
singing during some ceremonial songs (Elmore
1976). The Navajo would also use the flower
heads to clean cactus fruits of their spines.
Allred, K.W. 2002. A Working Index of New
Mexico Vascular Plant Names. New Mexico
State University. http://web.nmsu.edu/~kallred/
herbweb/ [not paged].
Comstock, J.P., T.A. Cooper, and J.R. Ehleringer.
1988. Seasonal patterns of canopy development
and carbon gain in nineteen warm desert shrub
species. Oecologia, Berlin 75(3): 327-335.
Cooper, R.A., R.J. Bowers, C.A. Beckham, and
R.J. Huxtable. 1996. Preparative separation of
pyrrolizidine alkaloids by high-speed counter
current
chromatography.
Journal
of
Chromatography 732(1): 43-50.
Dick-Peddie, W.A. 1993. New Mexico
Vegetation: Past, Present and Future. University
of New Mexico Press, Albuquerque, NM. 244 p.
Ehleringer, J.R. and T.A. Cooper. 1992. On the
role of orientation in reducing photoinhibitory
damage in photosynthetic-twig desert shrubs.
Plant Cell and Environment 15(3): 301-306.
Elmore, F.H. 1976. Shrubs and Trees of the
Southwest Uplands. Southwest Parks and
Monuments Association, Tucson, AZ. 214 p.
Epple, A.O. 1995. A Field Guide to the Plants of
Arizona. Falcon Publishing Inc., Helena, MT.
347 p.
Gay, C. W., Jr. and D. D. Dwyer. 1998 Reprint.
New Mexico Range Plants. Cooperative
Extension Service Circular 374. Revisions by:
C. Allison, S. Hatch, and J. Schickedanz. New
Mexico State University, Las Cruces, NM. 84 p.
Ivey, R.D. 1995. Flowering Plants of New Mexico,
3rd Edition. Published by the author, NM.
504 p.
Kartesz, J.T. 1994. A Synonymized Checklist of
the Vascular Flora of the United States, Canada,
and Greenland, Vol. 1, 2nd Edition. Biota of
North America Program of the North Carolina
Botanical Garden. Timber Press, Portland, OR.
622 p.
Kearney, T.H., R. Peebles, and Collaborators.
1951 with 1960 supplement. Arizona Flora.
University of California Press, Berkeley, CA.
1,085 p.
Kirkpatrick, Z. M. 1992. Wildflowers of the
Western Plains. University of Texas Press.
Austin, TX. 240 p.
Martin, W.C. and C.E. Hutchins. 1980-1981
(reprinted 2001). A Flora of New Mexico. Vol.
2. Bishen Singh Mahendra Pal Singh (India) and
Koeltz Scientific Books (Germany). p. 1,2772,591.
Phillips Petroleum Company. 1963. Pasture and
Range Plants. Phillips Petroleum Co.,
Bartlesville, OK. 176 p.
Stegelmeier, B.L., J.A. Edgar, S.M. Colegate, D.R.
Gardner, T.K. Schoch, R.A. Coulombe, and R.J.
Molyneux. 1999. Pyrrolizidine alkaloid plants,
metabolism and toxicity. Journal of Natural
Toxins 8(1): 95-116.
Stubbendieck, J., S.L. Hatch, and C.H. Butterfield.
1997. North American Range Plants, 5th Edition.
University of Nebraska Press, Lincoln, NE.
501 p.
Turner, B.L. and T.M. Barkley. 1990. Taxonomic
overview of the Senecio flaccidus complex in
North America, including Senecio douglasii.
Phytologia 69(1): 51-55.
U.S. Department of Agriculture, Forest Service.
1937 (1988 Dover edition). Range Plant
Handbook. Dover Publications Inc., New York.
816 p.
Warnock, B.H. 1974. Wildflowers of the
Guadalupe Mountains and the Sand Dune
Country, Texas. Sul Ross State University,
Alpine, TX. 176 p.
_________________________________________
James E. Nellessen, Botanist, Biologist and
Environmental Scientist, Taschek Environmental
Consulting, 8901 Adams St., NE, Albuquerque,
NM 87113